Cleanup some type annotations. (ros2#392)

Certain versions of mypy complain that these annotations
are not being used, since the annotations are only in
comments.  But we use the "inline" types everywhere else,
so switch this over to the same thing, which should remove
the warning.

Signed-off-by: Chris Lalancette <clalancette@gmail.com>

Author: clalancette

launch_ros/launch_ros/actions/load_composable_nodes.py

@@ -85,7 +85,7 @@ def __init__(
         super().__init__(**kwargs)
         self.__composable_node_descriptions = composable_node_descriptions
         self.__target_container = target_container
-        self.__final_target_container_name = None  # type: Optional[Text]
+        self.__final_target_container_name: Optional[Text] = None
         self.__logger = launch.logging.get_logger(__name__)
 
     @classmethod

launch_ros/launch_ros/utilities/evaluate_parameters.py

@@ -157,7 +157,7 @@ def evaluate_parameters(context: LaunchContext, parameters: Parameters) -> Evalu
     :param parameters: normalized parameters
     :returns: values after evaluating lists of substitutions
     """
-    output_params = []  # type: List[Union[pathlib.Path, Dict[str, EvaluatedParameterValue]]]
+    output_params: List[Union[pathlib.Path, Dict[str, EvaluatedParameterValue]]] = []
     for param in parameters:
         if isinstance(param, ParameterFile):
             # Evaluate a list of Substitution to a file path